From 3633bc0358f947e027e7e471b1038d8d0380f477 Mon Sep 17 00:00:00 2001
From: Sutou Kouhei <kou@clear-code.com>
Date: Mon, 7 Jul 2025 10:10:19 +0900
Subject: [PATCH] Fix wrong Encoding resolution

In this context, `Encoding` means `REXML::Encoding` not `Encoding`.
---
 lib/rexml/encoding.rb |  2 +-
 test/test_source.rb   | 21 +++++++++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)
 create mode 100644 test/test_source.rb

diff --git a/lib/rexml/encoding.rb b/lib/rexml/encoding.rb
index da2d70d6..f8459316 100644
--- a/lib/rexml/encoding.rb
+++ b/lib/rexml/encoding.rb
@@ -5,7 +5,7 @@ module Encoding
     # ID ---> Encoding name
     attr_reader :encoding
     def encoding=(encoding)
-      encoding = encoding.name if encoding.is_a?(Encoding)
+      encoding = encoding.name if encoding.is_a?(::Encoding)
       if encoding.is_a?(String)
         original_encoding = encoding
         encoding = find_encoding(encoding)
diff --git a/test/test_source.rb b/test/test_source.rb
new file mode 100644
index 00000000..b309105a
--- /dev/null
+++ b/test/test_source.rb
@@ -0,0 +1,21 @@
+require "rexml/source"
+
+module REXMLTests
+  class TestSource < Test::Unit::TestCase
+    def setup
+      @source = REXML::Source.new(+"<root/>")
+    end
+
+    sub_test_case("#encoding=") do
+      test("String") do
+        @source.encoding = "UTF-8"
+        assert_equal("UTF-8", @source.encoding)
+      end
+
+      test("Encoding") do
+        @source.encoding = Encoding::UTF_8
+        assert_equal("UTF-8", @source.encoding)
+      end
+    end
+  end
+end